Method and apparatus for applying a fluid coating



Sept. 16, 1969 R. KORNER ET AL METHOD AND APPARATUS FOR APPLYING A FLUIDCOATING Filed July 11. 1966 M R R w x O T- 2 TO PER secowo SPEED UP 40TO 200 REM.

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PAUSE IN TILT PHOSPHOR [SLURRY l0 T0 60 secouos FIG.4.

40 T0 200 RPM.

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IITO 15 PER sscouo RESUMED TILT T! LT STOPPED WITNESSES United StatesPatent 3,467,059 METHOD AND APPARATUS FOR APPLYING A FLUID COATING RenzoL. Korner, Horseheads, and Himanshu M. Patel,

Cayuta, N.Y., assignors to Westinghouse Electric Corporation,Pittsburgh, Pa., a corporation of Pennsylvania Filed July 11, 1966, Ser.No. 564,203 Int. Cl. Bc 11/14 US. Cl. 118-53 4 Claims ABSTRACT OF THEDISCLOSURE This invention relates to a method and apparatus for rotatingand tilting a panel of a color television tube to apply a liquid coatingthereto and removing the excess coating material therefrom by spinningoff of the panel and collecting the excess on a rotating collectormember. A second stationary collector member is associated with therotating collector and the excess liquid drains into the stationarycollector from the rotating collector.

This invention relates to a method and apparatus for applying a fluidcoating to a foundation member and recovering the excess fluid.

One specific embodiment of the invention is that in which a phosphorslurry is applied to the face plate panel of a cathode ray tube in themanufacture of color television tubes.

In one method of manufacturing color cathode ray tubes, the phosphorscreen is disposed on the surface of the face plate portion of the tubeby depositing the phosphor slurry on the panel and then swirling thephosphor slurry over the face plate. The face plate panel consists ofthe viewing or face plate portion of the cathode ray tube and a rim orflange extends substantially perpendicular to the face plate portion.The rim and the face plate portion are normally referred to as the faceplate panel. This face plate panel is sealed to the funnel portion ofthe tube after certain manufacturing steps.

In the method mentioned above in which the phosphor slurry is swirledover the surface of the face plate, the normal process is to first mountthe face plate panel such that the viewing portion is substantiallyhorizontal with the rim extending upwardly. The phosphor slurry whichnormally includes a phosphor of one color as well as a water solublephotoresist or light sensitive material is then dispensed on the upperor inner surface of the face plate panel. The phosphor slurry may bepoured onto the central portion of the face plate and the slurry is thenswirled over the surface by rotating and tilting the face plate panel.The excess slurry is removed by gravitational and centrifugal forces andnormally washed away and lost. The slurry coating is then normally driedby suitable techniques such as infrared heat and then exposed toultraviolet light. The areas of the phosphor and photoresist coatingwhere the light strikes become hard due to the presence of photoresistand adhere to the face plate. The ultraviolet light renders thephotoresist material in the exposed areas insoluble in water, whereas inthe unexposed areas the photoresist retains its solubility in water. Thepanel is then Washed in water to remove the undesiredphosphor-photoresist covered areas which are the unexposed areas andthen the desired pattern of phosphor remains as is well known in theart. This phosphor screen is then dried and the above method is repeatedfor the other color phosphors to produce a multi-color phosphor screen.

In this prior art technique, the process is wasteful insofar as allowingthe expensive excess phosphor slurry to be lost. This is particularlytrue in view of some of the recent developments in phosphors in whichcertain of the phosphors are more expensive. Another problem is thatcertain of the materials in the phosphor slurry create a problem as faras the affluent water treatment.

Accordingly, it is the general object of this invention to provide a newand improved method of coating a foun dation member with a fluid andrecovering the excess fluid.

It is another object to provide a new and improved apparatus for coatinga foundation member with a liquid and recovering the excess liquid.

It is a more particular object of this invention to provide an improvedmethod and apparatus for coating a color television viewing screen witha phosphor slurry and recovering substantially all of the excessphosphur slurry for reuse.

Briefly, the present invention accomplishes the above cited objects byproviding apparatus for rotating and tilting a foundation member ontowhich a liquid coating is to be applied and in which a first collectoris mounted about the foundation and rotates and tilts with saidfoundation for collecting the excess liquid after coating the foundationmember. The excess liquid is removed by gravitational and centrifugalforces. A second collector member mounted about said first collectormember tilts with the apparatus but does not rotate and collects theexcess liquid collected by the first collector. The excess liquid isremoved from said first collector by centrifugal and gravitationalforces. The excess liquid is removed from said second collector bygravity flow.

These and other objects and advantages of the present invention willbecome more apparent when considered in view of the following detaileddescription and drawings, in which:

FIGURE 1 is an elevational view of a filming machine, partlydiagrammatic, embodying this invention;

FIG. 2 is an enlarged sectional view of a portion of FIG. 1;

FIG. 3 is a diagrammatic view illustrating a face plate panel in theinitial load or phosphor slurry dispensing position;

FIG. 4 is a diagrammatic view illustrating the face plate panel in asecond position after the coating is applied and just prior to removalof excess slurry;

FIG. 5 is a diagrammatic view illustrating the face plate panel in athird position after substantial removal of excess phosphor slurry torotating collector; and

FIG. 6 is a diagrammatic view illustrating the face plate panel in afourth position after and final phase of operation.

Referring to FIGS. 1 and 2, the filming and drying machine has a base 10which is normally secured to the floor and is provided with two uprightmembers 11 between which is rotatably supported a horizontal shaft 12.The shaft 12 has a spur gear 14 attached to one end thereof and ismeshed with a worm gear 15 driven by an electric motor 16 which rotatesthe shaft 12 about its horizontal axis. The electric motor 16 iscontrolled by a suitable timing means illustrated by the block 18.Mounted to the shaft 12 is a tubular support member 20 which is in turnsecured to a non-rotating cylindrical collector member 22. The members20 and 22 are rigidly secured to the shaft 12 and rotate therewith.

A rotary shaft 24 is also secured to the shaft 12 and rotates therewithand the shaft 24 also rotates about its own axis. The shaft 24 is drivenby a motor 26 which is controlled by suitable timing means 28. The endof the shaft 24 extends through the support member 20 and the shield 22and is secured to a turntable 30. The turntable 30 consists of adisk-like base 32. Mounting lugs 34 are provided on the base 32 forattaching and securing a rectangular or cylindrical tube face panel 36to the base 32. In the specific device shown, mechanical means are shownfor securing and holding the tube panel 36 but it is, of course, obviousthat a vacuum chuck or any suitable means may be used holding the tubeface panel 36. The base member 32 is a circular disk and mounted 'at theperiphery of the base 32 is a rotating collector member 40 which isrigidly secured to the base 32 and rotates therewith. The collector 40is tubular in shape and of greater diameter than base 32 and tapersinwardly to form a frustoconical configuration. The larger diameter endsof the collector 40 surrounds the base 32 with an annular space 42provided therebetween. The larger diameter end of the collector 40extends below the upper surface of the base 32. The smaller diameter endof the collector 40 extends above the upper surface of the panel 36.Mounting members 44 are secured to the base 32 and the inner surface ofthe collector 40 for securing the member 40 to the base 32. The annularspace 42 which is provided at the lower portion of the turntablesurrounding the outer periphery of the base 32 permits any liquid thatis thrown from the tube panel 36 onto the collector 40 to leave thecollector 40 through this annular space 42.

The liquid leaving the turntable 30 will be collected by thenon-rotating collector 22. The collector 22 is cylindrical in shape andprovided with an aperture 46 in one section thereof to permit liquidcollected therein to be drained from the non-rotating collector 22. Thecollector 22 which is substantially L-shaped in cross section isprovided with an annular base portion 50 below the base 32 andsubstantially parallel to the base 32 and extending from its innerdiameter adjacent the outer periphery of the base 32 to beyond thecollector 40. An upwardly extending flange 52 is provided on the innerperiphery of the base portion 50 and an upwardly extending flange 54 isprovided on the outer periphery of the annular base member 50.

The operation of the machine is best illustrated by FIGS. 3, 4, and 6.The tube panel 36 is mounted as illustrated in FIGS. 1, 2 and 3 whereinthe table 30 is in a horizontal position. The phosphor slurry consistingof suitable materials such as phosphor (zinc sulfide), polyvinylalcohol, ammonium dichromate and water is introduced into the centerportion of the tube panel 36. The amount of the liquid may be about 150cc. and about 20 percent of this slurry will be required to coat thetube panel 36. The tube panel 36 is then rotated at a speed of about 2to 20 rpm. by motor 26 and simultaneously the tube is tilted forwardfrom its horizontal position at a rate of A to 1 per sec. by motor 16.This is illustrated in FIG. 3. The face panel 36 continues this movementuntil it rotates to an angular position 20 to 30 from where it started.This is illustrated in FIG. 4. A pause in tilting of from to 60 sec.duration now takes place during which rotation is increased to 40 to 200r.p.m. Tilting then resumes at a rate of 1 to per sec. as shown in FIG.5 until a total angular displacement of from 80 to 120 is reached asshown in FIG. 6. Rotation and forced drying is continued for another 2to 4 minutes.

The phosphor slurry flows from the inner portion of the panel 36 andcoats the inner surface during the operation between FIG. 3 and FIG. 4.During the opera- 4 tion as represented between FIG. 4 and FIG. 5, theexcess phosphor slurry is thrown over the upper edge of the panel 36 andis collected on the inner surface of the rotating collector 40. In thatthe rotating collector 40 is a portion of a cone instead of a cylinder,centrifugal force is added to the gravitational force to drive the spunexcess phosphor slurry downward toward the opening 42. The opening 42permits the slurry to spin and drain off onto the non-rotating collector22 and is collected therein. The phosphor slurry will flow within thefixed shield 22 by gravitational forces to the aperture 46 provided inthe lower portion of the shield 22 when tilted. This liquid may then becollected in a container provided below and the material thus collectedmay be reused.

It should be noted that when the slurry arrives at the rotatingcollector 40, it is subjected to centrifugal force. Under thiscondition, the droplets of slurry can not exist as individual droplets.The centrifugal force will flatten the droplets immediately so that nobuildup can take place. This is an important feature because the thickerthe slurry accumulation on the rotating shield 40, the more likelyflaking will result. Flaking is undesirable because the particles couldruin the screen if they were to land on the screen surface.

We claim as our invention:

1. A filming apparatus for coating a liquid on a tube panel comprising atube panel holder for holding said tube panel, means for rotating andtilting said tube panel holder, a rotatable collector member providedabout said tube panel and secured to said tube panel holder forcollecting excess liquid from said tube panel when said tube panel andsaid rotatable collector are rotated by said means at a speed to throwsaid excess liquid from said tube panel, an opening in the lower portionof said rotatable collector member for draining said excess liquid fromsaid rotatable collector, and a non-rotatable collector surrounding saidrotatable collector for collecting said excess liquid drained from saidrotatable collector and permitting gravity flow of said excess liquidfrom said non-rotatable collector.

2. The filming apparatus as described in claim 1 in which the innersurface of said rotatable collector is frusto-conical surface with theenlarged end facing inwardly.

3. The filming apparatus as described in claim 1 in which said openingis annular.

4. The filming apparatus as described in claim 3 in which saidnon-rotatable collector is provided with an aperture through which saidexcess liquid flows from said filming apparatus.

References Cited UNITED STATES PATENTS 2,054,155 9/1936 Dulken 118-55 X3,364,054 1/ 1968 Weingarten. 3,376,153 4/1968 Fiore.

DAVID KLEIN, Primary Examiner US. Cl. X.R.

